Despite multi-modality treatment of an aggressive nature, the median survival in high-grade gliomas, especially glioblastoma multiforme is less than a year, and cure is generally anecdotal. These tumors have usually extended beyond the limits of a complete surgical resection and a dose of conventional external beam radiotherapy has been limited by surrounding brain tolerance. By placing radioactive seeds of Iodine 125 directly into the tumor bed, we can achieve a high radiation dose to the tumor, at a sharp fall-off of radiation to the surrounding normal brain, and thereby achieve an increased therapeutic ratio by delevering at low dose rates.